1. Field of the Invention
The present invention relates to a decladding method and a decladding device for removing cladding tubes (fuel pins) from spent nuclear fuel so that fine fragments of the spent nuclear fuel are obtained.
2. Description of the Prior Art
A fast breeder reactor uses a multiplicity of fuel pins as a nuclear fuel assembly and, therefore, it is necessary to take out the spent nuclear fuel from the fuel pins.
In order to remove the fuel pins from the spent nuclear fuel, prior art examples are disclosed, for example, by the Japanese laid-open patent application 1994-43288 and a publication, “Preliminary Scripts, pages 524 and 525, Autumn General Meeting, 2002, of the Atomic Energy Society of Japan, Sep. 14 to 16, 2002, at the Iwaki Meisei Univ.”. Therein, a method is employed in which the spent nuclear fuel assembly is sheared and the spent nuclear fuel is dissolved by nitric acid so that the nuclear fuel is separated from the fuel pins.
In order to shear the nuclear fuel assembly, a large size shearing machine having a hydraulic apparatus is needed. Also, the shearing is of a press-cutting type so that no fine shearing can be done, and shearing of a length size of only 2 to 4 cm can be done. Thus, it is not easy to take out the spent nuclear fuel from the sheared fuel pins.
In the prior art method of dissolving the spent nuclear fuel by nitric acid for separation, as mentioned above, a large amount of nitric acid is needed and also nitrogen oxides (NOx) are generated from the nitric acid by dissolving the spent nuclear fuel. Further, a denitration apparatus must be added to the facility for recovering the nitric acid. Moreover, in order to recover the nitric acid, a large amount of expense is incurred.
Thus, in reprocessing the spent nuclear fuel, a technology to efficiently remove the fuel pins from the spent nuclear fuel is desired.